Russia joined Western leaders on Friday in urging Libyan leader Muammar Gaddafi to step down and offered to mediate his departure, in an important boost to NATO powers seeking to end his 41-year rule.

It was a striking change in tone from Kremlin criticism of NATO air strikes in Libya, which are officially intended to protect civilians in a civil war but have effectively put the West on the side of rebels seeking Gaddafi’s removal.

NATO said it was preparing to deploy attack helicopters over the Arab North African state for the first time to add to the pressure on Gaddafi’s forces on the ground.

But his security forces demonstrated once again that they are far from a spent force, launching rocket attacks overnight on the rebel-held town of Zintan and fighting insurgents on the outskirts of the city of Misrata.